New growth protects fire areas from major mudslides

NORTH COUNTY —— On a recent sunny morning in the rugged hills
east of Valley Center, hard-hatted repair crews were preparing to
reopen Hellhole Canyon Open Space Preserve, one of 23 county-run
parks scorched by the Cedar and Paradise fires in October 2003.

"After the fire, this entire area was barren; you could just
walk straight through," district parks manager Mike McFedries said
at an overlook point close to the entrance of the preserve. "Now,
there are plenty of bushes to step around."

Those plants are important for many reasons, not the least that
their roots hold dirt in place and counteract the kind of erosion
and mudslides that regularly plague areas of California after
wildfires.

A dry winter after the 2003 fires caused little damage to the
scorched landscape left after the Cedar and Paradise fires. Still,
North County residents uneasily wondered if this winter's
record-breaking downpours would cause mudslides in the burn
areas.

As it's turned out, inland North County has avoided mudslides
like those that killed more than a dozen people in a San Bernardino
County canyon last Christmas for several reasons, parks managers,
geologists and forestry specialists said last week.

The winter rain did inflict substantial damage on San Diego
County parks, but erosion occurred far enough away from inhabited
areas to pose little danger to residents, officials said.

A year of regrowth made all the difference, they added.

In most places, the Cedar and Paradise fires burned so fast that
vegetation wasn't completely killed in 2003 and new sprouts were
able to take advantage of this year's rains. Spurred by the
third-wettest winter in San Diego County history, rapid regrowth of
vegetation has protected many blackened slopes against
mudflows.

"If we'd had 22 inches of rain right after the fire, we would
have been in serious trouble," said Kevin Quinn, drainage
supervisor for the city of Poway, where 54 homes burned in the
Cedar fire. "The vegetation did have a chance to catch up."

Satellite survey

Just after the 2003 fires, geologists and erosion specialists
identified a number of spots in unincorporated San Diego County
that could be vulnerable to mudflows.

Working for the county, GeoSyntec Consultants used satellite
imaging to compile a list of target sites, said consultant Carol
Forrest, who did similar work after the 1991 Oakland and 1993
Malibu fires.

Surveyors followed up in helicopters and on foot, she said.
Federal officials also performed surveys for National Forest,
reservation and Bureau of Land Management lands.

Burned areas with steep slopes and unstable soils that posed an
immediate threat to public safety were quickly treated with mulch
—— a mixture of wood fibers, seeds and soil-stabilizing bacteria,
Forrest said.

A spreadsheet provided to the North County Times by Geosyntec
lays out how the firm decided on the highest-priority sites.

For example, after the Paradise fire —— which started near
Valley Center and burned through 56,700 acres —— the firm
identified eight sites of concern above Woods Valley Road, Paradise
Mountain Road and slopes east and west of Lake Wohlford as highest
in mudflow hazard.

The 270,000-acre Cedar fire started in the Cleveland National
Forest near Eagle Peak road, burned through Harbison Canyon and
eventually extended as far west as Poway and Scripps Ranch.
Geosyntec's survey identified 30 sites of high risk in the Cedar
fire area, dominated by Harbison Canyon and Wildcat Canyon.

Millions spent on flood controls

County officials said the number of mudflow hazard areas was
reduced this winter because of the county's extensive flood control
efforts. Starting in the winter after the fires, crews installed
the mulch, fiber barriers designed to disintegrate after a year,
and concrete barriers in some places, said Chandra Wallar, the
county's assistant director of public works.

Rains last October helped identify problematic areas that needed
beefing up this winter, such as steep slopes above San Diego
Country Estates east of Ramona and near Dehesa Road in Harbison
Canyon, Wallar said.

The county Public Works Department spent around $2.2 million to
protect private residences and $1.3 million for roadways from soil
erosion in the winter of 2003-04, but that number dwindled to
around $60,000 this winter. It also used $1 million in federal
money for flood control projects this winter, officials said.

The county parks department spent more than $3.2 million on
debris removal, trail restoration and erosion control in the months
after the 2003 fires and an additional $1 million to repair rain
damage this winter.

The Poway Public Works Department has struggled to keep silt
from clogging storm pipes and culverts at the eastern edge of the
city, said Quinn, the city's drainage supervisor. Runoff draining
into Rattlesnake and Sycamore creeks has flooded nearby roads this
winter, costing the city about $100,000, he said.

Fire too fast

Back at Hellhole Canyon, parks manager McFedries drove along
grooved mud roads last week, pointing out an area next to a stream
where live oaks with blackened trunks had begun to sprout again
from their branches.

The Paradise fire swept through the remote park so quickly that
trees weren't burned down to the root ball and so recovery has
begun, he noted.

Still, it's been an on-and-off process. The park, which is close
to where the Paradise fire started Oct. 26, 2003, reopened last
year in April. It then closed in October 2004 after heavy rains
washed out its steep roads and paths. In preparation for a
reopening scheduled for May, California Conservation Corps crews
have been using wheelbarrows to haul in gravel and
bowling-ball-size rocks to rebuild trails.

McFedries contrasted the wind-whipped Paradise fire with a
slower-moving wildfire in 2002 that burned 62,000 acres near
Julian. That blaze, called the Pines fire, completely destroyed
trees and seeds in the area. The trees burned in the Pines fire
will not recover and what was forest will convert to grassland,
McFedries predicted.

The Cedar fire was also mostly wind-driven, but in the last few
days of its progress, trees also burned hotter and longer at Rancho
Cuyamaca State Park, causing more sustained damage, he added.

Even as vegetation recovers, county parks managers are working
to clear out streambeds that have filled with sand and rock. When
it's not raining, water now flows under the bed of accumulated
sediment rather than on top, so animals have less access to flowing
water, McFedries said.

"We've had a record fire, record drought and then record-setting
rains, all in the last 18 months," he said. "It's hard to plan
ahead for events like that."

Rain too slow

Landslide experts at the U.S. Geological Survey said last year
that heavy rains in fire-blackened areas could trigger flows
powerful enough to carry large trees and even boulders downhill ——
a worry to residents in homes below those picturesque rocks.

Despite the abundance of precipitation this winter in San Diego
County, the rain didn't reach the intensity necessary to trigger
widespread flows, USGS researcher Sue Cannon said this week.

In a burned area, a quarter-inch of rainfall per hour would be
dangerous and a half-inch per hour would raise a flash flood
warning, she said.

None of the experts could say what the rate of downpours were
this winter, except that they vary by location. The only thing for
sure is that there was plenty of rain: A state forestry rain gauge
in Julian recorded 12 inches of rain last winter and 32 this
winter.

What has caused the landslides under houses in Carlsbad and
Oceanside —— a different phenomenon than mudslides or debris flows
—— is soil saturated by sustained rain over weeks or months, Cannon
said.

In general, inland San Diego County has solid weathered granite
rather than more erosion-vulnerable clays or sedimentary rock found
along the coast, she said.

After the deluge

At least one inland family was forced out of its home because of
the rains. In October, flooding and mud pushed Robin McMahon and
her family out of their house on Pappas Road in the San Diego
Country Estates development southeast of Ramona.

The McMahons moved back about a week ago, after the county
installed a huge drain under their house, leading runoff from their
back yard into the street.

The bottom floor of the house was "gutted and then completely
remodeled," she said.

The drain was paid for by the county Public Works Department,
which used $1 million from the federal National Resource
Conservation Service to install flood control measures such as
drains and concrete channels around the county, including 10 sites
in San Diego Country Estates.

The McMahons seem to have been the only family in Ramona or San
Diego Country Estates pushed out by runoff from a fire-scarred
slope, California Department of Forestry and Fire Protection Chief
Michael Vogt said.

"There's still lots of mud; it just goes into the cul-de-sac
(now) rather than into the back yard and the house," McMahon
said.